The present invention relates to catalytic systems and temperature-swing adsorption systems, more particularly to catalytic oxidation systems that operate at higher temperatures than temperature-swing adsorption systems.
The fuel onboard a submarine is the ultimate source of all energy produced and consumed on the submarine. Refueling a nuclear powered submarine is very costly and produces radioactive hazardous waste. The United States Navy seeks to reduce the refueling requirement of its nuclear and non-nuclear submarine fleet. In the nuclear case, an ultimate goal would be to produce a submarine which is fueled once during manufacture with enough fuel to last for the life of the submarine. One way to reduce the fueling requirement on the submarine is to reduce the amount of power that the submarine generates and consumes. Consequently, any modification to any equipment that reduces the amount of energy consumed is beneficial to the US Navy.
U.S. Navy submarines are equipped with devices for removing carbon monoxide (CO), carbon dioxide (CO2), and other contaminants from the air contained in the enclosed space. Catalyst systems and CO2 removal systems are implemented as separate systems onboard a submarine. A catalytic burner (synonymously referred to herein as a catalytic oxidizer) is a device that effects catalyzed chemical reactions so as to break down molecules of hazardous airborne contaminants to convert them to non-hazardous molecules, namely CO2 and water vapor. The catalyst within the burner system must operate at an elevated temperature in the range of ˜450-600° F., and the burner system must consume electrical power from the submarine to maintain this catalyst operating temperature. The catalyst burner also generates waste-heat which requires additional energy from the submarine for waste-heat removal. All of this contributes to the overall power consumed on the submarine and the requirement to consume fuel. The CO2 removal unit that is currently onboard submarines is a scrubber system based on an aqueous solution of monoethanol amine (MEA). The scrubber system operates at steady-state wherein CO2 is removed from the air and absorbed into the MEA solution at a low temperature (˜70° F.) and subsequently removed from the MEA solution at a higher temperature (˜250° F.). The CO2 removal system also consumes energy and generates undesirable waste-heat on the submarine. With the current operating parameters of these systems, there is no way to reduce the total amount of energy consumed and waste-heat generated by combining these systems.
A new carbon dioxide (CO2) removal system based on sorbents, known as the Advanced Carbon Dioxide Removal Unit (ACRU), is being developed by the U.S. Navy. The ACRU represents a type of temperature-swing adsorption system that is propitiously applicable to removal of carbon dioxide from confined environments such as those existing onboard submarines and other vessels. According to the ACRU, adsorption of CO2 occurs at room temperature (˜70° F.), and desorption of CO2 occurs at ˜180° F. Whereas the liquid MEA system operates at steady-state with the MEA in a continuous loop, the ACRU must cycle two or more sorbent beds between the low adsorption temperature and high desorption temperature in a non-steady state manor. When a sorbent bed must be regenerated, heat input is required to raise its temperature from the adsorption temperature to the desorption temperature. When the sorbent bed must be cooled, heat removal is required.